Magnetic correlations in subsystems of the misfit [Ca${}_2$CoO${}_3$]${}_{0.62}$[CoO${}_2$] cobaltate

Abstract

[Ca${}_2$CoO${}_3$]${}_{0.62}$[CoO${}_2$], a two dimensional misfit metallic compound, is famous for its rich phases accessed by temperature, $i.e.$ high temperature spin-state transition, metal-insulator transition (MIT) at intermediate temperature ($\sim$ 100 K) and low temperature spin density wave (SDW). It enters into SDW phase below T${}_{MIT}$ which becomes long range at 27 K. Information on the independent role of misfit layers (rocksalt/Ca${}_2$CoO${}_3$ \& triangular/CoO${}_2$) in these phases is scarce. By combining a set of complementary macroscopic (DC magnetization and resistivity) and microscopic (neutron diffraction and X-ray absorption fine structure spectroscopy) measurements on pure (CCO) and Tb substituted in the rocksalt layer of CCO (CCO1), magnetic correlations in both subsystems of this misfit compound are unraveled. CCO is found to exhibit glassiness, as well as exchange bias (EB) effects, while CCO1 does not exhibit glassiness, albeit it shows weaker EB effect. By combining local structure investigations from extended X-ray absorption fine structure (EXAFS) spectroscopy and neutron diffraction results on CCO, we confirm that the SDW arises in the CoO${}_2$ layer. Our results show that the magnetocrystalline anisotropy associated with the rocksalt layer acts as a source of pinning, which is responsible for EB effect. Ferromagnetic clusters in the Ca${}_2$CoO${}_3$ affects SDW in CoO${}_2$ and ultimately glassiness arises.

7 pages, 8 figures and supplementary file

References in corpus (7)

• Controlling orbital moment and spin orientation in CoO layers by strain
• Spin correlations and cobalt charge states: A new phase diagram of sodium cobaltates
• Anisotropic Susceptibility of La_2-xSr_xCoO_4 related to the Spin States of Cobalt
• Charge and spin order on the triangular lattice -- Na${}_x$CoO${}_2$ at $x=0.5$
• Local Structure of Thermoelectric Ca3Co4O9
• Origin of the high Seebeck coefficient of the misfit [Ca${}_2$CoO${}_3$]${}_{0.62}$[CoO${}_2$] cobaltate from site-specific valency and spin-state determinations
• Nonlinear transport associated with spin-density-wave dynamics in Ca${}_3$Co${}_4$O${}_9$

Cited by in corpus (4)

• Crossover from itinerant to localized states in the thermoelectric oxide [Ca${}_2$CoO${}_3$]${}_{0.62}$[CoO${}_2$]
• Incommensurate and multiple-$\mathbf{q}$ magnetic misfit order in the frustrated quantum-spin-ladder material antlerite, Cu${}_3$SO${}_4$(OH)${}_4$
• Impurity-induced spin density wave in the thermoelectric layered cobaltite [Ca${}_2$CoO${}_3$]${}_{0.62}$[CoO${}_2$]
• Random magnetic anisotropy driven transitions in layered perovskite LaSrCoO${}_4$